A tilt-cab truck is known from Dutch patent application No. 72/15364 in which the system for tilting the vehicle cab from and into the drive position includes at least one double-acting hydraulic piston-cylinder device, a pump, a reservoir for the hydraulic fluid, and a control valve. The ends of the piston-cylinder device are pivotally connected to the vehicle's cab and to the vehicle's chassis, respectively, and there is a by-pass connection between the cylinder spaces on either side of the piston when the latter is in the region of its innermost position (corresponding the drive position of the cab). The by-pass connection permits the piston and therefore the cab when in the drive position, to perform a limited reciprocating movement while the pump is inoperative.
With tilt-cab trucks such as the one disclosed in the above-mentioned Dutch application, the tiltable cab is supported by springs while in the drive position. Due to the presence of the by-pass connection between the two cylinder spaces in the innermost piston position, the piston is permitted to follow the up and down elastic movements of the cab relative to the chassis, occurring during driving, with a corresponding inward and outward sliding movement relative to the cylinder. However, the tilt cylinders are no longer "on line" when the cab is in the over-the-road position, and the entire weight of the cab must be supported by the springs and/or other suspension and shock absorber elements.